dct16x16_test: add NEON functions

note not all functions have NEON implementations:
- fdct/fht/iht

Change-Id: I6bb7ffe89b8cc23b642e19caf22f04f2d5e39087

test/dct16x16_test.cc

@@ -512,6 +512,14 @@ INSTANTIATE_TEST_CASE_P(
         make_tuple(&vp9_fht16x16_c, &vp9_iht16x16_256_add_c, 2),
         make_tuple(&vp9_fht16x16_c, &vp9_iht16x16_256_add_c, 3)));
 
+#if HAVE_NEON
+INSTANTIATE_TEST_CASE_P(
+    NEON, Trans16x16DCT,
+    ::testing::Values(
+        make_tuple(&vp9_fdct16x16_c,
+                   &vp9_idct16x16_256_add_neon, 0)));
+#endif
+
 #if HAVE_SSE2
 INSTANTIATE_TEST_CASE_P(
     SSE2, Trans16x16DCT,